[vtk-developers] Re: [vtkusers] Removing lighting from points, lines, and wireframe

[J.A. Lee]

I'm for #3, make it an option.
-Jeff

David Pont wrote:

> I have experienced invisible (black) lines, so I would like to see 
> some option to manage this. Of the four options I would vote for "3) 
> Make it an option where the default is to not use lighting (1) but
> it could be turned on".
> Would it be more compatible to default to lighting on (the current 
> behaviour), but it can turned off? or is that already possible?.
>
> To digress: OpenGL provides the following material properties: 
> GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_EMISSION, GL_SHININESS. When 
> using OpenGL some years back (before I discovered vtk) I used the 
> EMISSION property at times to avoid lighting effects on surfaces. For 
> scientific visualisation this is arguably an essential option. While 
> shading is an important visual clue to shape, it can be misleading for 
> interpretation of colour as a representation of attribute data.
>
> vtkProperty provides: SetAmbient, SetDiffuse, SetSpecular, 
> SetSpecularPower, SetOpacity. Could a SetEmitted be added?. This could 
> be used in combination with SetAmbient etc to obtain the full range of 
> shading, including none. Or am I just misunderstanding and mis-using 
> lighting in general!
>
>  regards
>     Dave Pont
>
>
>> From: "Ken Martin" <ken.martin at kitware.com>
>> To: "Vtk-Developers at Public. Kitware. Com" 
>> <vtk-developers at public.kitware.com>, "Vtkusers at Public. Kitware. Com" 
>> <vtkusers at public.kitware.com>
>> Subject: [vtkusers] Removing lighting from points, lines, and wireframe
>> Date: Mon, 1 Oct 2001 12:04:13 -0400
>>
>> Hello Folk,
>>
>> We are considering removing lighting from points, lines, and wireframe
>> in VTK and I wanted to get some feedback on the idea. Currently
>> lighting is applied to a wireframe mesh by default and this frequently
>> causes confusion because parts of the mesh are black (or near black)
>> due to lighting considerations when they expect the mesh to show up.
>> The same thing happens less commonly for lines and points. One
>> suggestion is
>>
>> 1) remove lighting from lines, points, and wireframes
>>
>> 2) remove lighting from wireframes, but leave it on for points and
>> lines if they have normals
>>
>> 3) Make it an option where the default is to not use lighting (1) but
>> it could be turned on
>>
>> 4) leave it the way it is, I like my wireframes shaded
>>
>> Thanks
>> Ken
>>
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-- 
J.A. Lee
Software Engineer
Computational Dynamics North America
3 Schoolhouse Lane
Etna NH, 03750
ph: 603-643-9993 x109, fax: 603-643-9994